Advantages of Wave Winding Over Lap Winding

Wave winding posses certain advantages over lap winding. The main advantage of wave winding is requirement of lesser amount of conductor and carbon brushes. This is because the number of parallel path in wave winding is always 2, therefore two carbon brushes are only required.

A wave winding may be fitted with as many brushes as the number of poles. In such case, if one or more brushes develop poor contact with the commutator, the commutator machines continues to operate satisfactorily whereas this is not so in case of lap connected machines.

For obtaining better commutation a lap connected machines requires equalizer ring whereas it is not required in wave connected machines.

Since the number of parallel path in lap winding is equal to the number of poles, more carbon brushes and equalizer ring is required. This makes lap connected machine more costly. It also requires more maintenance.

Lap winding is used on low voltage medium power i.e. from 50 to 500 kW machines and high power machine above 500 kW power rating. Wave winding is used for high voltage and low power machine. It is generally used for machines having power rating less than 50 kW. The basic thumb rule is that, lap winding is used where the machine requires low voltage but more current whereas wave winding is suited where current is low but voltage is high.

The preferred choice of wave winding is due to the fact that wave winding do not require equalizer ring. As a consequence, wave wound dc machines are less expensive as compared to lap wound dc machine. However, for armature current more than 400 A, lap wound machine is the only choice as such a heavy current can be distributed among the parallel paths in lap wound machine without compromising good commutation. As there are only two parallel paths in wave wound machine, such heavy current may lead to poor commutation and reduction of machine life.

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